Plastic rubber product



' Punaaoa. 22, 1935 UNITED STATES 2.01am ms'rrc avenue 'monucr In Williams, Woodstm, and Carroll Cummings Smith, Carneys Point, N. 1., asslznors to E. I. du Pont de Nemoun & Company, Wilmington, DeL, acorporatlon of Delaware so 1mm. Application my 0, m4,

Serial sq. 13am as Claims. (01. iii-5o) This invention relates to rubber and more particularly to the preparation of more plastic rubber products.

In the preparation of rubber products, it is 5 usually desirable to have the rubber in a plastic condition soas to facilitate the processing operations. For example, it is desirable to have the rubber in a plastic condition when adding fillers, vulcanizlng ingredients and the like. 'It is also desirable to have the rubber in a plastic condition to facilitate shaping and molding of the rubber prior to vulcanization. It is well known that rubber,'when subjected to mechanical working such as is obtained by the use of a rubber mill, particularly in the presence of oxygen, is rendered much more plastic. vThe degree of plasticizing is determined to a great extent by the temperature and the time of milling. When milled for a suflicient length of time, the rubber 20 will become very soft. However, extended milling of rubber tends to'destroy the internal structure of the rubber and produces a final product of very inferior physical properties.

In order to reduce the time of milling and to 25 avoid the'deteriorating action of extended milling, it has become common practice to add to the rubber, during the milling operation, certain materials which assist in softening the rubber. Zl'he materials which are most commonly employed 30 are. oils, esters, waxes, fats, alcohols, acids, resins and the like which. assist in the production of soft rubber either by a swelling action on the rubber or by acting as a/lubricant. Some of the most common softe ers are mineral oil, pine tar, 5 palm oil-rosin 0', dibutyl phthalate, paraflin, glycerine, lauryl alcohol and stearic acid. It is also'known that certain chemicals, such-as diphenyl guanidine, have a slight softening action on the rubber while other chemicals, such as benzidine, have a considerable stiffening action.

Rubber which has been subjected to the action of swelling agents, such as mineral oil, kerosene I and similar materials, is softened merely by the distending action of the swelling material. The

45 degree of softening. and swelling by the use of these materials can be increased until the rubber" assumes the consistency of a soft jelly or cement.

When such rubber is compounded with the usual vulcanizing agents and vulcanized, the swelling rubber has a low modulus of elasticity and is inferior for many purposes.

Rubber is probably composed of micelles which, in turn, consist of a large number of molecules. The softness or plasticity of the rubber is largely 5 determined by the state of gelation and size of the micelles. Any reduction in the degree of as' sociatioir of the micelles or any means which will reduce the size of the micelle will result in a softening action. Such action is shown by certain accelerators, such as diphenyl guanidine, although the eigect is not great. The type of softening produced by the use of peptizing 'agentsis desirable because the effect is almost entirely destroyed dining vulcanization.

An object of the present inventionis to provide a class of materials which, when added to rubber, will produce a greater 'plas'ticizing action than those previously employed. A further obiect is to provide a class of materials which will cause a softening action on rubber when used in relatively small amounts without producing a material swelling or dissolving action on the rubber.

A still further object is to supply a class of plasticizers for rubber, the effect of which, is largely destroyed during vulcanization. Other 1 objects are to provide new compositions of matter and to advance the art. Still other oblectswill appear hereinafter.

These objects may be accomplished in accordance with our invention which comprises subjecting rubber to the action of small amounts of certain plasticizing agents for a sufllcient length of time for the rubber to attain the desired plasticity. The resulting compositions will be more plastic than other rubber compositions heretofore prepared, will produce products having improved physical properties and will be in a condition whereby they may be more easily worked in processing operations. 40

The plasticizing agents of our invention comprise a' class of salts of unsymmetrically substituted hydrazinesfhavingthe formula:

aralkyl or aryl nucleus; X represents hydrogen, one valence of a doubly bonded carbon atom, or an alkyl, aralkyl or aryl nucleus except that X must be,of a different class than R when R1 represents hydrogen; Y represents hydrogen or one valence of a doubly bonded carbon atom anddrogen; that X must not be alkyl when R is alkyl and R1 is hydrogen; and I must not be aralkyl when R is aralkyl and R1 is hydrogen. In other words, we specifically exclude from within the scope of our invention salts of compounds having the formula;

.wherein both R and X represent alkyl nuclei, or

represent aralkyl nuclei, or represent aryl nuclei.

One valence of a doubly bonded carbon atom, as employed in the specification and in the claims, will be understood-to include compounds in which both the X and the Y valences are connected to the same carbon atom as in compounds represented by the formula:

and to include compounds in which the valence is "of a carbon atom which is doubly bonded to some element other than carbon as in the compounds represented by the formula:

R of

Bi Y By the expression an alkyl, aralkyl or aryl nucleus, it will be understood that the indicated group is bonded to the nitrogen directly by means of a carbon atom of such nucleus.

Such nuclei may contain hydroxy, alkoxy, nitro, halogen or amino substituents. Also, the term alkyl will be understood to include both saturated and unsaturated aliphatic hydrocarbon nuclei.

It will thus be apparent that the compounds of our invention, in general comprise neutral and acid salts ,of mono substituted, asymmetrical disubstituted, unbalanced disubstituted: and trisubstituted hydrazines. The acidic substances which are employed to prepare the salts may be necessary to incorporate, in the rubber, a small 10 amount ofan agent of our invention. The plasticizing agents may be incorporated in the rubber by milling, employing the minimum amount of milling required for that purpose. The plast'iciizing agents may be applied to the surface of 15 thin sheets of rubber either by dipping in any of the agents which are liquids or in solutions of the agents or by spraying the liquids or solutions on thesurface of the rubber and even by dusting the solid compounds on the surface of 20 the rubber. When our agents are brought into contact with the surface of the rubber by any of such methods, the agent will diffuse into the rubber and exert its softening effect.

The change in the state of the rubber gel 25 induced by our compounds is not instantaneous but requires more or less time to develop. While a small immediate eifectmay result, it is, in general,-not great enough to be noticeable. After incorporatirig one of our compounds into the rub- 30 ber, the rubber soon becomes softenedand the softening action continues at a gradually decreasing rate until an apparent equilibrium is reached, after which, little or no softening action takes place. The length of time, required to reachthis 35 periods of time which may vary from 15 minutes to one or two days. 7

The amount of softening, which will be obtained over a given period of time, will vary with the amount of plasticizing agent which is employed. However, the increase in softening effect of increased amounts of agent is not in p'ro- 50 portion tothe amount of agent added. The amount of agent to be added may be varied within an extremely wide range, depending upon the rubber, the other compounding ingredients 7 and the desire of the user. However, for eco- 55 nomical reasons, it will generally .be found that from about .1 to about 5% of the agent will be suflicient for most purposes. Hence, it will be seen that the extent of the softening can be largely co'ntrolled by control of the time, temperature and concentration of'the plastlcizing agent. As a means of measuring the effectiveness of these materials forreducing theplasticity of rub--v ber, small amounts-of the various materials were incorporated into the rubber with the minimum 65 The results 01' such tests are shown in the'tollow- Asymmetrical methyl phenyl hydrazines ing table: Mono xylylhydrazines Table I Mono o-biphenyl hydrazines Mono hydroxy phenyl hydrazines m mm Mono benzyljhydrazines 5 r v m numb 4 Mono chlorphenyl hydrazines Mama mo Mono aminophenyl hydrazines n g mt. Com Mono anisyl hydrazines a trol Mono methyl hydrazines Mono lauryl hydrazines 1o Dichlorphenyl hydrazines 152%; diifittl'gt'lfit'y'm"""'::::::::: 1:22 1%, :it Nltwpheflvlhvdmmes henymdmm' 5 1% 1%; The above. hydrazines and other hydrazines g a: heretofore mentioned may be employed as the 1100 I245 I207 salts of any acid reacting compound which is suili-. 5 26 3m ciently strongly acid to react with the hydrazines oxenyl hydrazine sullate :50 to form the salts, Among the acidic substances eetsaststlsessleres -1; to 1% which may be wowed. to form the are m-nitro phenylhydrazine stearsts e 1.00 .267 .297 Ph 1 N,N b-hydroxy-etllyl phenylhydruine eno 1. 00 250 297 b-naphthol Asymmetric diphenyl hydrazine hthalate 1.0) .277 .297

Asymmgtr ig phenyl methyl ydrazlne- 1 m m m cresols Other salts which have proved to be particularly gm -gi naphthaenes efiective for our purpose are the reaction products Dmydmxy biphenyls of phenyl hydrazine and carbon dioxide, ethyl Fol-mic acid sulphon'yi derivative of 2:5-dichlorphenyl hydrasteal-1c acid zine and o-tolyl hydrazonium salt of the dithioe oxalic acid carb'amlc acid derived from o-tolyl hydrazine. Acetic acid In general, salts, which will be found effective Benzoiwacm for our purpose, may be prepared from the 101- phthalic acid lowing hydrazine's: propi'omc acid Phenylhydrazine Butyric acid o-tolyl hydrazine Oleic acid o-xenyl hydrazine Palmitic acid a-naphthyl hydrazine 'Sultonic' acids m-nitrophenyl hydrazine Naphthoic a N,N' B-hydroxy-ethyi phenyl hydrazine Phenyl benzolc acid 40 Asymmetrical diphenyl hydrazine Phenyl naphthoic acid Asymmetrical phenyl methyl'hydr'azine Nap thyl benzolc acid 2 :5-dichlorphenylhydrazine Nanhthyl naphthoic. acid Acetone phenyl hydraaone Halogen substitutedacids Asymmetrical di-lauryl hydrazine ch10! ficetlc Bclds (monoand N,N' phenyl benzyl hydrazine Anthranilic acids Mono-acetyl phenyl hydrazine Hydrochloric acid The thio urea resulting .irom the action of Ni ri ac phenyl mustard oil on phenyl hydrazine 8111111116 acid Benzoyl derivative of 2:5-dichlorphenyl hydra- Phosphoric acid 50.

zine I Sulphur dioxide p-nitrophenyl hydrazine Carbon dioxide Phenyl hydrazine. formaldehyde reaction prod- E y ul acid t 4 l Dithiocarbamic acid of phenyl hydrazine Methyl propyl ketone phenyl hydrazone Dithlocarbamic acid of o-tolyl hydrazine Other hydrazines whose salts merit special atother ditmwarbami" acids tentmn It will be apparent that a wide variety of hydrazine salts may be. employed. Within the Asymmetrical -t y yd e limits or the type rot-mule:

Asymmetrical dl-lwlyl hydrazines 80 Asymmetrical di-biphenyl hydrazines Asymmetrical di-naphthyl hydrazines N-N A Asymmetrical phenyl tolyl hydrazines Asymmetrical phenyl hiphenyl hydrazines I V A y r a p y nsp t rlh d w s .as defined herelnberore, the components R, R1 05 Asy m toly n yl hydrazlnes and x may-represent methyl. ethyl. propyl. but l. Asymmetrical di-benzyl hydrazines lsobutyl, tertiary butyL'am'y iw my al y (1 Asymmetrical p nyl benz l hym tyi, butylene, lauryl; stearyl or other saturated A ymm ric l dl-hydroxyphenyl y or unsaturated alkyl group or may be benzyl, ring. Asymmetrical di-chlorphenyl hydrazines ub titut d be'nzyl, naphthyl methyl or other Asymmetrica1 di-p-aminophenyl hydrazines.

- Asymmetrical phenyl phenol hydrazines Asymmetrical tolyl phenol hydrazines Asymmetrical di-ani'syl hydrazines Asymmetrical phenyl anisyl hydrazlnes aralkyl groups or may be. substituted or unsubstltuted aromatic radicals such as dimethylphenyl, ethylphenyl, nitrophenyl, chlorphenyl,

'- aminophenyl, chlornaphthyL nitronaphthyl, al-, *kylnaphthyl, biphenyl, alkylbiphenyl, chlorbi- 4 a,o1a,e44

. phenyl, nitrobiphenyl, aminobiphenyl, cyclohexyl,

and the like, orother groups which are generally known to be aliphatic or aromatic innature. The hydrazines disclosed herein are, in general, well known compounds and the methods of preparing the same are also well known and described inv the literature The salts, may be formed simply by bringing the hydrazine and the required acidic substance into intimatecontact or by fusing them together. Since the hydrazines are only weakly basic, the'i'ormation of the salts is sometimes accomplished in a more favorable manner by carrying out the'faddition in a non-aqueous solvent such as dry benzene and the like, particularly, in the absence of water. For this reason, itis obvious that, for the purpose ofthis invention, the hydrazine and the acid may be added to the rubber separately and the required salt formed within the rubber. For

example,- we have found that phenyl hydrazine will combine with stearic acid more readily in benzene solution and that o-tolylhydrazine will unite with oxalic acid more readily in ether solution. In a similar manner, we have found the phenylhydrazine and stearic acid may be added I separately to the rubber and still produce a,de-

Any acidic substance,

sirable softening action. either organic or inorganic of a strength sunlci'ent to form a salt under such circumstances, may be employed to form the corresponding sal which will be effective for our purpose.

While we have disclosed the preferred embodiments of our invention, it will be readily apparent to those skilled in the art that manychanges and variations may be made therein without departing from the spirit of our invention. Accordingly, the scope. of our invention is to be limitedsolely by the appended claims construed astbroadly as is permissible in view of the prior. ar

. We claim: I

1. Unvulcanized rubber of increased plasticity obtainable by subjecting the rubber to action of a salt of an unsymmetrically substituted hydranucleus; 31 represents hydrogen or an .alkyl, aralkyl or aryl nucleus; 2! represents hydrogen,

one valence of a doubly bonded carbon atom, or

an alkyl, aralkyl or aryl-nucleus, except that 1:

must be of a diflerent class than B when R1 represents hydrogen; Y represents hydrogen or one valence of a doubly bonded carbon atom; and A represents one equivalent of a salt-forming acid-- reacting compound, for a suflicient length of time to produce increase in the plasticity of the rubber. v K

2. In the process of making rubber articles, the

step which comprises subjecting 'unvulcanized rubber to the action of a salt of an unsymmetrically substitutedhydrazine, which salt has the formula a wherein R represents an alkyi, aralkyl or aryl 'nucleus; R1 represents hydrogen or an 'alkyl,

aralkyl or aryl nucleus; x represents hydrogen,

one valence of a doubly bonded carbonatom, or

- rubber to the action of a salt of an unsymmetrically substituted hydrazine containing at the most 3 substituent groups, in which each of the substituent groups is an organic group having a carbon atom thereof directly bonded to a 5 nitrogen, of the hydrazine" nucleus, for a sufficient length of time to produce an increase in the plasticity of the rubber. 4. In the process of making rubber articles the step which comprises subjecting .unvulcanized 20 rubber to the action of a salt of an unsymmetrically substituted hydrazine containing at .the'most 2 substituent groups, in which .each of the substituent groups is an organic group having a carbon atom thereof directly bonded to a nitrog5 gen of-the hydrazine nucleus, for asuflicient length of time. to produce an increase in the plasticity of the rubber. a 5. In the process of making rubber articles, the

- step which comprises subjecting unvulcanized rubber to the action of a salt of a mono-substituted hydrazine, in which the substituent is an organic group having a carbon atom thereof directly bonded to a nitrogen of the hydrazine nucleus, for a sufficient length of time to produce 35,

an increase in the plasticityof the rubber,

7 6. In the process of making rubber articles, the step which comprises sub ecting unvulcanized' rubber to the action of a t ofa mono-substituted hydrazine, in which the substituent is 40 an aromatic group having a carbonatom thereof directly bonded to'a nitrogen of the hydrazine nucleus, for a suflicient length of time to produce an increase inthe plasticity of the rubber.

7. In the processor making rubber articles, the

step which comprises subjecting unvulcanized rubber to the actionof a salt of an unsymmetrically di-substituted hydrazine, in which each substituent is an organic group having a carbon atom thereo'f directly bonded to a nitrogen ofgthe hydrazine nucleus. for a suflicient length of time to produce an-increase in thev plasticity of the rubber.

8. In the process .of making rubber articles the step which comprises subjecting unvulcanized' rubber to the action of a salt of an asymmetrical di-substitutedhydrazine, in which each suir stituent is an organic group having a carbon atom thereof directly bond to a nitrogen of the hydrazine nucleus, for a to produce an increase in the plasticity of the rubber.

9. In the process of making rubber articles, the step which comprises subjecting unvulcanized rubber to the action of asalt ofan asymmetrical cient length of.time so] aromatic directly bonded to one nitrogen of the hydrazine nucleus and the other substituent.

is an aliphatic radical having a carbon atom thereof directly bonded to the other nitrogen of the hydrazine nucleus, fora suflicient length of time to produce'an increase in the plasticity of the rubber.

I 11. In the process of making rubber articles, the step which comprises subjecting unvulcanized rubber to the action of a salt of aninorganlc acid and an unsymmetrically substituted hydrazine which salt has the formula wherein R represents an alkyl, aralkyl or aryl nucleus; R1 represents hydrogen'or an alkyl, aralkyl or aryl nucleus; X represents hydrogen,

one valence of a doubly bonded carbon atom, or

an alkyl, aralkyl or aryl nucleus, except that X i must be of a different class than R when R1 represents hydrogen; Y represents hydrogen or one valence of a doubly bonded carbon atom; and A represents one equivalent of an inorganic acid,

for a sufficient length of time to produce an in-" crease inthe plasticity of the rubber.

12. Inthe process of making rubber articles, the step which comprises subjecting unvulcanized rubber to the action of a salt of an inorganic acid and an unsymmetrically substituted hydrazine containing at the mosh 2 substituent groups, in,

to produce an increase in the plasticity of the rubber.

14. In the process of making rubber articles, the step which comprises subjecting unvulcanized rubber to the action of a salt of an inorganic acid and an unsymmetrically disubstituted hydrazine, in which each substituent is an organic group having a carbon atom thereof directly bonded to a nitrogen-.01 the hydrazine nucleus, for a suiilcient lengthlof time to produce an increase in the plasticity of the rubber.

15. In the process of making rubber-articles, the step which comprises subjecting \unvulcanized rubber to the action of a salt of an organic acid and an unsymmetrically substituted hydrazinewhich salthasthe formula w n -x 1 p. n B|/.

resents hydrogen; Y represents hydrogen or one valence of a doubly bonded carbon atom; and A represents one equivalent of an organic acid, for

& a suiilcient length of igme to produce an increase in the plasticity of the rubber.

16. In the process of-making rubber articles, the step which comprises subjecting unvulcanized rubber to the action of a salt of an organic acid 5 and an unsymmetrically substituted hydrazine containing at the most 2 substituent groups, in which each of the substituent groups is an or-. ganic group having a carbon atom thereof'directly bonded. to a nitrogen of the hydrazine nucleus, for a suflicient length oftime to produce an increase in the plasticity of the rubber.

17. In the process of making rubber articles, the step which comprises subjecting unvulcanized rubber to the action of a salt of an organic acid 13 and a mono-substituted hydrazine, in which the substituent is an organic group having a carbon atom thereof directly bonded to a nitrogen of the hydrazine nucleus, for a suflicient length of time to produce an increase in the plasticity of the 0 rubber.

18. In the process of making rubber articles, the step which comprises subjecting unvulcanized rubber to the action of a salt of an organic acid and an unsymmetrically di-substituted hydrazine, 25

in which each substituent is an organic group hav ing a carbon atom thereof directly bonded to a nitrogen of the hydrazine nucleus, for a sufiicient length of time to produce an increase in the plasticity of the rubber.. 80 w 19;. Unvulcanized rubber of increased plasticity obtainable by subjectingthe rubber to the action of a salt of an unsymmetrically substituted hydrazine containing at the most 3 substituent groups, in which each of the substituent groups is an 35 organic group having a carbon atom thereof directly bonded to a nitrogen of the hydrazine nucleus, for a sufficient length, of time to produce an increase in the plasticity of the rubber.

20. Unvulcanized rubber of increased plasticity 40 obtainable by subjecting therubber to the action of a salt of an unsymmetrically substituted hydrazine containing at the most 2 substituent groups, in which each of the substituent groups is an organic group having a carbon atom thereof 45 directly bonded to a nitrogen of the hydrazine nucleus, for a suflicient length of time to produce an increase in the plasticity of the rubber. 21. Unvulcanized rubber or increased plasticity obtainable by subjecting the rubber to the action 50 group having a carbon atom thereof directly bond ed to a nitrogen of the hydrazine nucleus, for a 'suflicient length of time to produce an increase in the plasticity of the rubber.

23. Unvulcanized rubber of increased plasticity obtainable by subjecting'the rubber to the action of a salt of an inorganic acid and an unsymmetri- 'cally substituted hydrazine which salt has the formula n r N-n A wherein Rrepresentsanal kyl, aralkyl,oraryl nucleus; R1 represents lwdrogen or an alkyl,

a suilicient length of time to produce an increase in the plasticity of the rubber.

24. Unvulcanized rubber of increased plasticity obtainable by subjecting the rubber to the action of a salt or an inorganic acid and an unsymmetrically substituted hydrazine containing at the most 2 substituent groups, in which each oi! the substituent groups is an organic group having a carbon atom thereof directly .bonded to a nitrogen.

of the hydrazine nucleus, tor a suiilcient length of time to produce an increase in the plasticity of the rubber. r

25. Unvulcanized rubber or increased plasticity obtainable by subjecting the rubber to the action 01' a salt of an organic acid and-an unsymmetrically substituted hydrazine which salt has the formula Bi V Y 7}. wherein It represents an alkyl, aralkyl or aryl nucleus; R1 represents hydrogen or an alkyl,

aralkyl or aryl nucleus; 1! represents hydrogen,

one valence. of a doubly bonded carbon atom,

or an alkyl, aralkyl or aryl nucleus, except that X must be oi! a diflerent class than B. when R1 represents hydrogen; Y represents hydrogen or 5 obtainable by subjecting the rubber to the action of a salt of an organic acid and an unsymmetrically substituted hydrazine containing at the most 2 substituent groups, in which each .of the substituent groups is an organic group having a 15 carbon atom thereof directly bonded to a nitrogen 0! the hydrazine nucleus, for a su'fllclent length or time to produce 'an' increase in the plasticity of the rubber 27. In the process of making'rubber articles, 20 the step which comprises subjecting the unvulcanized rubber to the action of phenylhydrazine oxalate tor a sufllcient length of time to produce an increase in the plasticity of. the rubber.

28. In the process of making rubber articles, 25 the step which comprises subjecting the unvulcanized rubber to the action of phenylhydrazine hydrochloride for a suiiicie'nt length of time to pro-. duce an increase in the plasticity of the rubber.

CARROLL 0. SMITH. 

